The present invention is a reconstituted, protein enriched, sweetened, reduced lactose milk product, in the general area of dairy products.
Milk contains only one carbohydrate, lactose. Lactose, or milk sugar, is a disaccharide consisting of the monosaccharides glucose and galactose. Disaccharides cannot be absorbed in the intestine. In most people, an enzyme called lactase is produced which hydrolyses, or splits, lactose into glucose and galactose.
When a person is lactase deficient, they are unable to hydrolyze the lactose to produce glucose and galactose for use as an energy source. The absorption of the other nutrients in the milk is also interfered with. Lactose intolerant people, those people who produce insufficient lactase, suffer substantial physical distress from the production of gas, cramping, and diarrhea due to ingestion of dairy products and subsequent fermentation of the undigested lactose by bacteria residing in the intestine.
Lactose intolerance is found throughout the world. It appears to be the result of genetic factors, age, and perhaps environment. There is a higher incidence of lactose intolerance in people residing in Africa, the Far East and around the Mediterranean and their descendants. The ability to produce lactase declines with age. The highest levels of lactase are produced in children at the time of birth, decreasing through adolescence to levels as low as ten percent of their initial values by the time a person reaches adult age.
Lactose deficiency is treated either by avoidance of all dairy products or treatment of the dairy product with lactase, either before or simultaneously with ingestion. At the present time, lactase is produced commercially by companies including Sturge Enzymes, Selby, North Yorkshire, England, Novo Enzymes, Bagsvaerd, Denmark, Gist-Brocades N.V., Delft, Holland, and Chas. Pfizer Co., Inc. New York, New York. The lactase produced by these particular companies is derived from a yeast common to the dairy industry, Kluyveromyces fragilis. Enzyme activity is defined in units (EU), that amount of lactase which produces one micromole of glucose per minute from lactose at pH 6.2, usually at a temperature of 30.degree. C., although this varies with the company.
Lactase, also known as beta-D-galactosidase E.C. 3.2.1.23, is most stable at pH's between about 6 and 9, with optimum activity at pH 6.2. Activity declines rapidly at a pH below about 5.5 and higher than about pH 7.5. The temperature at which the enzyme is maintained also significantly affects activity and stability. The enzyme rapidly declines in stability at temperatures in excess of about 45.degree. C. Lactase requires the presence of two types of cations for maximum effect. Mn.sup.++ is the most effective divalent cation, activating at 10.sup.-5 to 10.sup.-4 M. Mg.sup.++ has a somewhat effect at 10.sup.-30 to 10.sup.-2 M. Zn.sup.++ and Co.sup.++ also activate the enzyme. At higher concentrations, a monovalent cation is required. 0.1 M K.sup.+ is most effective, with NH4.sup.+ and Na.sup.+ having some effect. Ca.sup.++ does not activate the enzyme. Fe.sup.++ inhibits the enzyme, as do quaternary ammonium compounds.
Lactase is routinely added to such dairy products as milk and milk products, fermented dairy products, and whey, whey protein concentrate and whey permeate. The primary reason lactase is added to milk and milk products is to increase their digestibility by lactose-intolerant people. In frozen dairy products, as well as in highly concentrated whey-derived dairy products, lactase is used to produce the monosaccharides which are more soluble and less subject to crystallization than the lactose which causes the frozen or concentrated product to have an undesirable texture. In fermented dairy products such as yogurt, lactase is added to increase the sweetness of the product by converting the lactose to glucose and galactose, without having to add additional sugar.
On a practical basis, the addition of lactase to milk or other dairy products does not yield a 100% lactose free product. With respect to refrigerated milk, lactase is added either by the consumer in his home to a carton of milk which is then mixed well and allowed to sit overnight in the refrigerator before using, or by the dairy prior to pasteurization and packaging. Pasteurization denatures the enzyme so that no further reduction in the level of lactose is achieved. The usual result in both cases is that only about 70% of the lactose is hydrolyzed.
An alternative system has been developed by Tetra Pak, Lausanne, Switzerland. In this system, milk is first sterilized using an ultraheat treatment process consisting of a brief heat shock, approximately 4-8 seconds, preferably 4 seconds, at approximately 140.degree. C. This treatment kills all of the bacteria in the milk. Milk sterilized by this process can be packaged aseptically and maintained for several weeks at room temperature. In the system developed by Tetra Pak, lactase is added to the ultraheat-treated milk prior to packaging via a sterile pump and filter assembly. Since refrigeration is not required, nor any further heat treatment, the enzyme is able to hydrolyze the lactase in the package over several days, resulting in a product containing very little, if any, undigested lactose. Several advantages to the use of lactase to reduce lactose in milk or milk-derived products is readily apparent. In those situations where adequate refrigeration is not a problem, lactase-treated dairy products are available which can be digested by those who would otherwise be deprived of the nutritional advantages of dairy products, as well as the taste of ice cream, milk, cheese, yogurt, sour cream, etc. The Tetra Pak product can be used in those situations where refrigeration is not available or where a product which is 100% lactose free is required.
Unfortunately, the product produced using the ultraheat treatment has one major drawback, particularly when prepared from reconstituted milk. It tastes terrible.
It is therefore an object of the present invention to provide a good tasting, reduced lactose dairy product.
It is another object of the present invention to provide a good tasting, reduced lactose dairy product which does not require refrigeration.
It is a still further object of the present invention to provide a high protein, high vitamin, high mineral, greater than 99% fat-and lactose-free dairy product made using powdered dry milk.